In the prior art, several approaches have been used in an interexchange network to identify the service logic that needs to be executed to process a particular service request. One prior approach connects telephone user equipment subscribing to a particular service directly to a dedicated interexchange trunk group so that the interexchange network can identify the requested service and thus the service logic that needs to be executed to process an associated service call. However, such an approach is not economical, since most service subscribers do not provide a sufficient level of traffic (or demand) to use optimally the capacity of a dedicated trunk group.
Another prior approach attempts to optimize trunk usage by associating a trunk group, and thus the service logic, with a combination (set) of network services. Although such optimization is somewhat economical, it is not flexible. That is, in order to obtain a desired service a telephone user has to subscribe to a combination of such services, some of which the telephone user might find to be undesirable.
As is well-known, a variety of signaling protocols are used to establish connections between switching exchanges (i.e., local and toll offices). One such protocol is the well-known Signaling System 7 (SS7). The SS7 protocol has been defined by Study Group XI - Specification of Signaling System No. 7, International Telegraph and Telephone Consultative Committee (CCITT) Blue Book, Vol. 6 of Facile VI.9, Geneva, Switzerland, 1989. The SS7 protocol provides, inter alia, a method by which a local exchange office transmits a code known as Automatic Number Identification (ANI) to a toll office, in which the ANI identifies the originator (i.e., line circuit) of a call that the former office is forwarding to the latter office. The ANI code, as well as the called telephone number, are transmitted in a signaling message or packet commonly referred to as an Initial Address Message (IAM), which contains other information necessary for the toll switch to complete the call. Since an IAM contains ANI information identifying the source of a telephone call, it appears that a specific network service associated with a telephone call could be identified at a toll switch by merely examining the ANI information contained in the associated SS7 message.
However, such an approach is not always practical. The reason for this is that a toll switch would have to check the ANI information accompanying each incoming call to determine if the call is associated with a particular service and/or feature. Since a toll switch processes a very large number of incoming calls, the additional task of checking the ANI information associated with each incoming call would increase the load on the call processing resources of the toll switch.